The present invention relates to the technical field of a color correcting method in which the dispersion of the spectral sensitivity characteristic of an image reading apparatus is corrected when an original image is photoelectrically read and appropriate colors can be reproduced in accordance with the original image. The invention also relates to the technical field of an image reading apparatus performing this color correcting method.
At present, most of the images recorded on photographic films such as negatives and reversals (which are hereinafter referred to as xe2x80x9cfilmsxe2x80x9d) are printed onto light-sensitive materials (photographic papers) by a technique generally called xe2x80x9cdirect exposurexe2x80x9d (analog exposure) in which the light-sensitive materials are exposed with the light projected from the films.
In contrast, printers which adopt digital exposure have recently been commercialized. In this xe2x80x9cdigital photoprinterxe2x80x9d, the image recorded on a film is read photoelectrically and converted into digital signals, which are subjected to various kinds of image processing to produce recording image data; a light-sensitive material is scanned and exposed with recording light modulated in accordance with the image data, thereby recording a (latent) image which is then made to a (finished) print (photograph).
The digital photo printer is basically composed of a scanner (image reading apparatus) for photoelectrically reading images recorded on a film, an image processing apparatus for subjecting the image data read with the scanner or the image data supplied from a digital camera or the like to preset image processing and making the image data to image data for recording images, that is, setting exposure conditions based on the image data, a printer (image recording apparatus) for recording a latent image by scanning and exposing a light-sensitive material with, for example, a light beam in accordance with the image data output from the image processing apparatus, and a processor (developing apparatus) for subjecting the light-sensitive material having been exposed with the printer to development processing and for outputting prints on which the images are reproduced.
In the digital photoprinter, since an image can be made to digital image data and exposure conditions used in printing can be determined by subjecting the digital image data to image processing, prints of high quality, which cannot be obtained by the conventional direct exposure, can be obtained by preferably executing the correction of washed-out highlights and dull shadows due to photography with back light or an electronic flash, sharpening processing and the like. Further, a plurality of images can be composited to a single image or one image can be split into segments through the image processing. In addition, prints can be outputted after they are optionally subjected to editing and processing in accordance with the use of them.
Further, according to the digital photoprinter, not only images recorded on a film can be output but also prints, on which images recorded on a printed matter, a photograph and the like are reproduced, can be output by connecting a scanner (image reading apparatus) for reading a reflecting original to the digital photoprinter.
Incidentally, in the scanner of the digital photoprinter and the scanner for the reflecting original, reading light is incident on an original, and projected light, which has passed through the original (film), or reflected light, which has been reflected from the original, is read with an image sensor such as a CCD sensor or the like, thereby photoelectrically reading original images.
Further, the projected light and the reflected light of the original are processed with red (R), green (G) and blue (B) color filters or reading light processed with the R, G and B color filters is incident on the original, whereby the original images are read by being separated into the three primary colors R, G and B.
In the above situation, when scanners of the same type read the same original, they must obtain the same image signals (image data).
However, illuminants, color filters, image sensors and the like which are mounted on scanners are somewhat different from each other in the arrangement, quality and the like. As a result, each of the scanners has a spectral sensitivity characteristic particular to it even if they are of the same type. Accordingly, since resultant image signals reflect the spectral sensitivity characteristic of each scanner, images having different color tints are produced with each scanner even if visible images are reproduced using the image signals. Thus, appropriate colors cannot be always reproduced in accordance with the original, that is, an image of high quality cannot be always reproduced.
An object of the present invention is to solve the problem of the prior art and to provide a color correction method by which the dispersion of the spectral sensitivities of scanners caused by illuminants, color filters and the like (reading error caused by the dispersion) can be preferably corrected and uniform colors can be reproduced, and to provide an image reading apparatus making use of the color correction method.